Hand tool comprising a sensor for emitting a signal when the tool attachment is replaced

ABSTRACT

The invention is based on a hand power tool, in particular a manually operated right angle grinding machine or a manual circular saw, with a driver mechanism ( 12 ), which can operatively connect an inserted tool ( 16 ) to a drive shaft ( 18 ). 
     The invention proposes that at least one sensor ( 10 ) can detect at least one procedural step in the changing of an inserted tool ( 16 ) and can produce a signal.

BACKGROUND OF THE INVENTION

The invention is based on hand power tool.

In order to be able to advantageously connect an inserted tool to adrive shaft of a machine tool by means of a tool holding fixture, it isknown to affix the drive shaft to a locking device.

For right angle grinders, a locking device is known that has a lockingbolt, which is guided in a housing so that it is rotationally fixed inrelation to the drive shaft and which, by means of an actuating button,can be brought into engagement with a gearing that is non-rotatablyconnected to the drive shaft.

In addition, EP 0 904 896 A2 has disclosed a grinding machine toolholding fixture for a manually operated right angle grinding machine.The right angle grinding machine has a drive shaft, which has a threadoriented toward the tool.

The grinding machine tool holding fixture has a driver and a retainingnut. In order to install a grinding wheel, the driver is slid with amounting opening onto a collar of the drive shaft and by means of theretaining nut, is clamped in a frictionally engaging manner to asupporting surface of the drive shaft. Oriented toward the tool andextending in the axial direction, the driver has a collar that hasrecesses on its outer circumference, on two radially opposing sides,which extend axially to a base of the collar. A groove extends on theouter circumference of the collar, counter to the drive direction of thedrive shaft, starting from each of the recesses. The grooves are closedcounter to the drive direction of the drive shaft and taper axiallystarting from the recesses, counter to the drive direction of the driveshaft.

The grinding wheel has a hub with a mounting opening, which contains twoopposing tabs pointing radially inward. The tabs can be inserted axiallyinto the recesses and then introduced circumferentially into thegrooves, counter to the drive direction. By means of the tabs in thegrooves, the grinding wheel is fixed in a form-fitting manner in theaxial direction and is fixed in a frictionally-engaging manner by thetapering contour of the grooves. During operation, the frictionalengagement increases due to the reaction forces acting on the grindingwheel, which act counter to the drive direction.

In order to prevent the grinding wheel from coming off when the driveris braking the drive shaft, in the vicinity of a recess on thecircumference of the collar, a stopper is provided, which is supportedso that it can move in the axial direction in an opening. In anoperating position with the grinding wheel pointing downward, thestopper is axially deflected toward the grinding wheel by the force ofgravity, closes the groove in the direction of the recess, and preventsthe tabs disposed in the groove from moving in the drive direction ofthe drive shaft.

SUMMARY OF THE INVENTION

The invention is based on hand power tool, in particular a manuallyoperated right angle grinding machine or a manual circular saw, with adriver mechanism, which can operatively connect an inserted tool to adrive shaft.

The invention proposes that at least one sensor, which is disposed inparticular in the vicinity of the driver mechanism, can detect at leastone procedural step in the changing of an inserted tool and can producea signal. An operation of the hand power tool can be prevented while theinserted tool is being changed and the safety can be increasedparticularly by virtue of the fact that the signal can prevent anoperation of the driver mechanism. A wide variety of sensors deemedappropriate by one skilled in the art can be used for the embodimentaccording to the invention, such as electrical, mechanical, and/orelectromechanical sensors, etc., which can produce a variety of signals,such as electrical, mechanical, optical, and/or acoustic signals, etc.

Furthermore, preventing the driver mechanism from operating can beachieved by variety of structural embodiments, for example by means of amechanical and/or electromechanical clutch, which can be combined with alocking device of a drive shaft. If the signal can interrupt a powersupply, for example by means of an electrical sensor and a switch, thenthis allows the operation to be prevented with a particularlyspace-saving and lightweight design.

It can also be advantageous if a light source can be switched by meansof the signal, for example a warning light, which notifies an operatorof a change, or a change that has not yet been completed, and/or anillumination of the driver mechanism, which can facilitate aninstallation and removal of an inserted tool in dark spaces.

In another embodiment, the invention proposes that the inserted tool canbe operatively connected to the driver mechanism by means of at leastone detent element, which is supported so that it can move in oppositionto a spring element and which engages in an operating position of theinserted tool and fixes the inserted tool in a form-fitting manner, andthat the sensor can detect at least one position of the detent element.The form-fitting engagement can achieve a high degree of safety and canproduce a simple and inexpensive tool-free quick-clamping system and thesensor can be easily integrated into it. The movement of the detentelement can be detected directly or indirectly by means of a componentmoved by the detent element. The inserted tool can be reliably preventedfrom unintentionally coming loose by means of the form-fittingengagement, even when the drive shaft is being braked, during whichintense braking moments can occur. Fundamentally, however, it is alsoconceivable that the sensor is actuated by means of a cable controland/or a lever mechanism, etc.

The movable support of the detent element permits a large deflection ofthe detent element during installation of the inserted tool, whichpermits a large amount of overlap between two corresponding detentelements and a particularly secure form-fitting engagement to beproduced and on the other hand, permits an easily audible engagementsound to be produced, which advantageously indicates to the operatorthat the desired locking procedure has been completed.

The movably supported detent element can be embodied in a variety offorms deemed appropriate by one skilled in the art, for example anopening, projection, pin, bolt, etc., and can be disposed on theinserted tool or on the driver mechanism. The detent element itself canbe movably supported in a component in a bearing, for example in aflange of the driver mechanism or in a tool hub of the inserted tool.The detent element, however, can also be embodied as connected by meansof frictional engagement, form-fitting engagement, and/or materiallyadhesive engagement to a component movably supported in a bearing or canbe of one piece with this component, for example a component supportedon the drive shaft or to a tool hub of the inserted tool.

Furthermore, the form-fitting engagement permits an advantageousencoding to be achieved so that only specifically intended insertedtools can be fastened in the driver mechanism. The driver mechanism canbe at least partially embodied as a detachable adapter piece or can bedetachably connected to the drive shaft by means of frictionalengagement, form-fitting engagement, and/or materially adhesiveengagement.

The detent element can be embodied so that it can move in variousdirections in opposition to a spring element, for example in thecircumference direction or in a particularly advantageous manner, in theaxial direction, which permits the achievement of a structurally simpleembodiment and a movement path that can be easily detected by thesensor.

A particularly inexpensive, rugged, and structurally simple embodimentcan also be achieved in that the detent element can actuate anelectrical switch element that constitutes the sensor. If the switchelement is disposed so that it cannot rotate in relation to a rotationaxis of the drive shaft or is affixed to the housing, then an additionalrotating mass and an expensive set of contact connections betweencomponents that rotate in relation to each other can be avoided. At thevery least, however, individual pieces can also be embodied so that theyrotate, for example in the vicinity of an actuating button.

In another embodiment, the invention proposes that the drive shaft canbe locked by means of an actuating button of a locking device in orderto change the inserted tool and that the sensor can detect a position ofthe actuating button. Additional components can be saved and a reliablesignal can be achieved. Fundamentally, however, it is also conceivablefor the signal be able to lock the drive shaft electrically and/orelectromagnetically, etc.

The invention also proposes that the actuating button is operativelyconnected to the drive shaft in the rotation direction and the actuatingbutton for locking the drive shaft can connect at least one first part,which is operatively connected to the drive shaft in the rotationdirection, to a second part that cannot rotate in relation to a rotationaxis of the drive shaft. Having the actuating button rotate with thedrive shaft during operation can reliably prevent the actuating buttonfrom being improperly used to slow down the drive shaft. A detachment ofinserted tool due to an unforeseen, powerful braking moment and anassociated injury risk can be reliably prevented and wear on the lockingdevice can be reduced.

The embodiment according to the invention can be used in a variety ofhand power tools deemed appropriate by one skilled in the art, forexample eccentric grinders, oscillating grinders, brushes, drills, etc.,but can be used to particular advantage in manual circular saws andright angle grinders in which uncontrollably rotating inserted tools cancause particularly serious injuries.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages ensue from the following description of the drawings.An exemplary embodiment of the invention is shown in the drawings. Thedrawings, the specification, and the claims contain numerous features incombination. One skilled in the art will also suitably consider thefeatures individually and will unite them to form other meaningfulcombinations.

FIG. 1 shows a top view of a right angle grinder,

FIG. 2 shows a schematic cross section along the line II—II in FIG. 1,through a grinding machine tool holding fixture according to theinvention, and

FIG. 3 shows a bottom view of a tool hub.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a top view of a right angle grinding machine with anelectric motor, not shown, contained in a housing 42. The right anglegrinding machine can be guided by means of a first handle 44 extendingthe longitudinal direction and integrated into the housing 42 on theside remote from a cutting wheel 16 and by means of a second handle 48extending lateral to the longitudinal direction and fastened to thetransmission housing 42 in the vicinity of the cutting wheel 16.

By means of a transmission that is not shown in detail, the electricmotor can drive a drive shaft 18, whose end oriented toward the cuttingwheel 16 is provided with a driver mechanism 12 (FIG. 2). On a sideoriented toward the cutting wheel 16, the driver mechanism 12 has adriver a flange 50 press-fitted onto the drive shaft 18 and on a sideoriented away from the cutting wheel 16, has a driver disk 40, which issupported so that it can be slid on the drive shaft 18 in opposition toa concentrically disposed helical spring 28.

Furthermore, three pins 52, which extend up from the supporting surface56 in the axial direction 38 and are evenly distributed in thecircumference direction 32, 34, are provided for axially fixing thecutting wheel 16 in the axial direction 38 in relation to a respectivedisk spring 102. At their ends oriented toward the cutting wheel 16, thepins 52 each have a head, which has a greater diameter than the rest ofthe pin 52 and at an end oriented toward the driver flange 50, have aconical contact surface 104 tapering in the axial direction 36 and acontact surface 104 a extending parallel to the supporting surface 56.

The driver a flange 50 constitutes an axial supporting surface 56 forthe cutting wheel 16, establishes an axial position of the cutting wheel16, and has openings 58 let into it in the vicinity of the pins 52. Inaddition, three axial through bores 60 are let into the driver flange50, which are evenly distributed over the circumference in thecircumference direction 32, 34.

The driver disk 40 that is movably supported on the drive shaft 18 hasthree bolts 30 press-fitted into it one after the other in thecircumference direction 32, 34, which extend in the axial direction 38toward the cutting wheel 16 and, with a part 24, protrude up from thedriver disk 40 in the axial direction 36 oriented away from the cuttingwheel 16. The helical spring 28 presses the driver disk 40 in thedirection 38 toward the cutting wheel 16, against the driver flange 50and the driver disk is supported against this driver flange. The bolts30 protrude through the through bores 60 and extend up from the driverflange 50 in the axial direction 38.

In addition, disposed in the center on the side oriented toward thecutting wheel 16, the driver mechanism 12 has a cup-shaped unlockingbutton, which is of one piece with the actuating button 22 of a lockingdevice 20 of the drive shaft 18. The unlocking button has three segments62, which are distributed evenly in the circumference direction 32, 34,extending in the axial direction 36 in relation to the movably supporteddriver disk 40 and which reach through corresponding recesses 64 of thedriver flange 50 and are secured against falling out in the axialdirection by means of a snap ring 66 inside the driver disk 40. Theunlocking button is guided so that it can move in the axial direction36, 38 in an annular recess 68 in the driver flange 50.

The cutting wheel 16 has a sheet metal hub 70, which is securelyconnected to and pressed onto a grinding device 72 by means of a rivetedconnection that is not shown in detail (FIG. 3). The tool hub could alsobe made of another material deemed appropriate by one skilled in theart, for example plastic, etc. The sheet metal hub 70 has bores 74, 76,78 in succession, distributed evenly in the circumference direction 32,34, whose diameter is slightly greater than the diameter of the bolts30. In addition, the sheet metal hub 70 has three oblong holes 80, 82,84 distributed evenly in the circumference direction 32, 34 andextending in the circumference direction 32, 34, each of which has anarrow region 86, 88, 90 and a wide region 92, 94, 96 produced by meansof a bore, whose diameter is slightly greater than the diameter of theheads of the pins 52.

The sheet metal hub 70 has a centering bore 98, whose diameter isadvantageously chosen so that the cutting wheel 16 can also be clampedby means of a conventional clamping system to a clamping flange and aspindle nut on a conventional right angle grinding machine. A so-calledbackward compatibility is assured.

When the cutting wheel 16 is installed, the cutting wheel 16 is slidwith its centering bore 98 onto a collar 54 formed onto the supportingsurface 56 of the driver flange 50, which radially centers the cuttingwheel 16 with its centering bore 98. The driver flange 50 can thusadvantageously absorb radial forces produced during operation withoutputting strain on the unlocking button 22.

Then the cutting wheel 16 is rotated until the pins 52 engage in theprovided wide regions 92, 94, 96 of the oblong holes 80, 82, 84 of thesheet metal hub 70. The sheet metal hub 70 pressing against thesupporting surface 56 of the driver flange 50 causes the bolts 30 to beslid into the through bores 60 and causes the driver disk 40 to be slidaxially counter to a spring force of the helical spring 28 on the driveshaft 18, in the direction 36 oriented away from the cutting wheel 16.The parts 24 of the bolts 30, which protrude up from the driver disk 40in the axial direction 36 oriented away from the cutting wheel 16, areeach slid into one of a number of pockets 26, which are distributed inthe circumference direction 32, 34 and are formed into a bearing cover100. The bearing cover 100 is screwed firmly into the transmissionhousing 46. The pockets 26 cannot rotate in relation to a rotation axisof the drive shaft 18 or in relation to the drive shaft 18 itself andare closed in the rotation direction, and the drive shaft 18 isform-fittingly locked in the circumference direction 32, 34 by means ofthe driver flange 50 and the bolts 30.

In the direction of the driver mechanism 12, in a pocket 26 of thebearing cover 100, a sensor 10 is disposed so that it cannot rotate inrelation to a rotation axis of the drive shaft 18 and can detect aninstallation and removal of the cutting wheel 16. When the bolt 30 isinserted into the pocket 26, the bolt 30 actuates an electrical switchelement 14 that constitutes the sensor 10. A signal is produced, whichinterrupts a power supply of the right angle grinder and reliablyprevents the right angle grinder or of the driver mechanism 12 fromoperating.

The pockets 26 are embodied so that they are open radially toward theinside, which can prevent them from becoming clogged with dirt and dust.The pockets 26 could also be advantageously embodied so that they areopen in the axial direction 36 oriented away from the cutting wheel 16.

A further rotation of the sheet metal hub 70 counter to the drivedirection 34 causes the pins 52 to be slid into the arc-shaped narrowregions 86, 88, 90 of the oblong holes 80, 82, 84. As a result, the pins52 are slid by means of the conical contact surfaces 104 axially in thedirection 38 counter to the force of the disk springs 102 until thecontact surfaces 104 a of the pins 52 overlap the edges of the oblongholes 80, 82, 84 in the arc-shaped narrow regions 86, 88, 90.

When assembled, the disk springs 102, by means of the contact surfaces104 a of the pins 52, press the cutting wheel 16 against the supportingsurface 56. In lieu of several disk springs 102, the pins can also beloaded by means of other spring elements deemed appropriate by oneskilled in the art, such as helical springs or a disk spring, not shown,which extends over the entire circumference. The exemplary embodimentwith the pins 52 supported so that they can move axially, isparticularly suited for thick tool hubs and/or tool hubs, which can onlybe elastically deformed slightly.

In an end position or in an achieved operating position of the cuttingwheel 16, the bores 74, 76, 78 in the sheet metal hub 70 come to restover the through bores 60 of the driver flange 50. Due to the springforce of the helical spring 28, the bolts 30 slide out of the pockets26, in the axial direction 38 toward the cutting wheel 16, engage in thebores 74, 76, 78 of the sheet metal hub 70, and fix this hub in aform-fitting manner in both circumference directions 32, 34. When theyengage, an engagement sound is produced, which is audible to theoperator and indicates that the tool is ready for operation.Furthermore, when the bolt 30 comes out of the pocket 26, the electricalswitch element 14 constituting the sensor 10 is actuated and the powersupply of the right angle grinder is switched back on.

A driving torque of the electric motor of the right angle grindingmachine can be transmitted from the drive shaft 18 to the driver flange50 in a frictionally engaging manner and can be transmitted from thedriver flange 50 to the cutting wheel 16 in a form-fitting manner bymeans of the bolts 30. Furthermore, a braking moment, which is directedcounter to a driving torque during and after the electric motor beingswitched off, can be transmitted in a form-fitting manner from thedriver flange 50 to the cutting wheel 16 by means of the bolts 30. Anunintentional detachment of the cutting wheel 16 is reliably prevented.The three bolts 30 distributed evenly in the circumference direction 32,34 achieve an advantageous, uniform distribution of force and mass.

In order to detach the cutting wheel 16 from the right angle grindingmachine, the unlocking button is pressed. The driver disk 40 is thenslid together with the bolts 30 by means of the unlocking button oractuating button 22, counter to the helical spring 28, in the axialdirection 36 oriented away from the cutting wheel 16, as a result ofwhich the bolts 30 move in the axial direction 36 out of their lockedposition and out of the bores 74, 76, 78 of the sheet metal hub 70. Atthe same time, the bolts 30 engage with their parts 24 in the pockets26, as a result of which the drive shaft 18 is form-fittingly locked inthe rotation direction 32, 34. As with the installation of the cuttingwheel, when the bolt 30 is inserted into the pocket 26, the electricalswitch element 14 constituting the sensor 10 is actuated by the bolt 30.A signal is produced, which interrupts the power supply to the rightangle grinder and reliably prevents an operation of the right anklegrinder or of the driver mechanism 12.

Then the cutting wheel 16 is rotated in the driving direction 34 untilthe pins 52 come to rest in the wide regions 92, 94, 96 of the oblongholes 80, 82, 84 and the cutting wheel 16 can be removed from the driverflange 50 in the axial direction 38. After the unlocking button isreleased, the helical spring 28 slides the driver disk 40, the bolts 30,and the unlocking button or actuating button 22 back into their initialpositions. When the bolt 30 comes out of the pocket 26, the electricalswitch element 14 constituting the sensor 10 is actuated and the powersupply of the right angle grinder is switched back on.

Reference Numerals 10 sensor 12 driver mechanism 14 switch element 16inserted tool 18 drive shaft 20 locking device 22 actuating button 24part 26 part 28 spring element 30 detent element 32 circumferencedirection 34 circumference direction 36 direction 38 direction 40component 42 housing 44 handle 46 transmission housing 48 handle 50driver flange 52 pin 54 collar 56 supporting surface 58 opening 60through bore 62 segment 64 recess 66 snap ring 68 recess 70 sheet metalhub 72 grinding device 74 bore 76 bore 78 bore 80 oblong hole 82 oblonghole 84 oblong hole 86 region 88 region 90 region 92 region 94 region 96region 98 centering bore 100 bearing cover 102 disk spring 104supporting surface

1. A hand power tool, with a driver mechanism (12), which canoperatively connect an inserted tool (16) to a drive shaft (18),characterized in that at least one electrical sensor (10) can detect atleast one procedural step in the changing of an inserted tool (16) andcan produce a signal, and the signal can prevent an operation of thedriver mechanism (12).
 2. The hand power tool according to claim 1,characterized that the signal can switch off a power supply.
 3. The handpower tool according to claim 1, characterized in that the drive shaft(18) can be locked in place by means of an actuating button (22) oflocking device (20) in order to change the inserted tool (16) and thatthe sensor (10) can detect a position of the actuating button (22).
 4. Ahand power tool, with a driver mechanism (12), which can operativelyconnect an inserted tool (16) to a drive shaft (18), characterized inthat at least one sensor (10) can detect at least one procedural step inthe changing of an inserted tool (16) and can produce a signal, and thesignal can switch a light source.
 5. A hand power tool, with a drivermechanism (12), which can operatively connect an inserted tool (16) to adrive shaft (18), characterized in that at least one sensor (10) candetect at least one procedural step in the changing of an inserted tool(16) and can produce a signal, and the inserted tool (16) can beoperatively connected to the driver mechanism (12) by means of at leastone detent element (30), which is supported so that it can move inopposition to a spring element (28), engages in an operating position ofthe inserted tool (16), and fixes the inserted tool (16) in aform-fitting manner, and that the sensor (10) can detect at least oneposition of the detent element (30).
 6. The hand power tool according toclaim 5, characterized in that the detent element (30) can be moved inthe axial direction (36) in opposition to the spring element (28). 7.The hand power tool according to claim 5, characterized in that thedetent element (30) can actuate an electrical switch element (14) thatconstitutes the sensor (10).
 8. The hand power tool according to claim7, characterized in that the switch element (14) is disposed so that itcannot rotate in relation to a rotation axis of the drive shaft (18). 9.A hand power tool, with a driver mechanism (12), which can operativelyconnect an inserted tool (16) to a drive shaft (18), characterized inthat at least one sensor (10) can detect at least one procedural step inthe changing of an inserted tool (16) and can produce a signal, thedrive shaft (18) can be locked in a piece by means of an actuatingbutton (22) of a locking device (20) in order to change the insertedtool (16) and that the sensor (10) can detect a position of theactuating button (22), the actuating button (22) is operativelyconnected to the drive shaft (18) in the rotation direction (32, 34) andthe actuating button (22) for locking the drive shaft (18) can connectat least one first part (24). which is operatively connected to thedrive shaft (18) in the rotation direction, to a second part (26) thatcannot rotate in relation to a rotation axis of the drive shaft (18).